1. Hypoxic Preconditioning Requires the Apoptosis Protein CED-4 in C
Hypoxic Preconditioning Requires the Apoptosis Protein CED-4 in C. elegans 
Nupur Dasgupta, Aditya M. Patel, Barbara A. Scott, C. Michael Crowder 
Current Biology 
Volume 17, Issue 22, Pages (November 2007)
DOI: /j.cub
Copyright © 2007 Elsevier Ltd Terms and Conditions

2. Figure 1
Hypoxic Preconditioning Protects C. elegans from Lethal Hypoxic Insults
(A and B) Time-lapse images of (A) hypoxia preconditioned versus (B) nonpreconditioned adult worms after a 20 hr recovery from a 20 hr hypoxic incubation (pO2 < 0.3%). Note well-moving preconditioned animals and immobile nonpreconditioned animals without tracks in the bacterial lawn.
(C) Preconditioning requires hypoxia, not just higher temperature or buffer. Preconditioning for 4 hr and then 20 hr recovery were varied by normoxic or hypoxic, 20° or 26°, in liquid or on agar incubations as noted. Bars represent mean ± SEM of three trials (>50 animals/trial). ∗p < 0.01 versus normoxic, 20°, agar condition (two-tailed t test).
(D and E) Onset and duration of protection by hypoxic preconditioning from hypoxic (D) or azide (E) killing. After a 4 hr HP incubation, animals were allowed to recover for varying times in room air at 20° on agar prior to a 20 hr hypoxic or 1 hr 0.5M azide killing incubation. ∗p < 0.01 versus zero HP recovery time (two-tailed t test). Data points represent mean ± SEM.
(F) Length of hypoxic incubation time required for producing HP. The length of the hypoxic preconditioning at 26° in buffer was varied and was followed 20 hr later by a 20 hr hypoxic killing incubation. ∗p < 0.01 versus no HP incubation (two-tailed t test).
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3. Figure 2
Hypoxia-Induced Pathological Cell Defects and Cell Death Blocked by HP
L1 larvae underwent no hypoxic incubation (Normoxia) or a 20 hr hypoxic incubation that was preceded by 4 hr HP (HP) or normoxic preconditioning (No HP). After a 24 hr recovery, surviving animals were scored for cell pathological defects. Scale bars represent 20 μm.
(A and D) Muscle nuclear pathology reduced by HP. Muscle nuclei were visualized by nuclear-localized GFP driven by a muscle-specific promoter, Pmyo-3. Hypoxia produces damaged myocytes seen as nuclear fragmentation (arrow) and nuclear loss (arrowhead) [5] that is reduced by HP (∗p < 0.01 versus “No HP,” mean ± SEM, n = 29 animals [No HP] and 44 animals [HP]).
(B and E) Axonal pathology reduced by HP. Touch sensory neurons were visualized by GFP driven by a touch-neuron-specific promoter, Pmec-4. Hypoxia produces axonal beading pathology (arrow) [5] that is reduced by HP (∗p < 0.01 versus “No HP,” mean ± SEM, n = 124 axons [no HP] and 116 axons [HP]).
(C and F) Necrotic cell death reduced by HP. Hypoxia produces necrotic cell death (arrow) [5] that is reduced by HP (∗p < 0.01 versus “No HP,” n = 29 animals [no HP] and 44 animals [HP]).
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4. Figure 3 The Apaf-1 Homolog CED-4 Is Required for HP
(A–E) Open symbols represent data for no-HP-treated animals; closed symbols represent HP-treated animals. Data are paired by trial with concurrent HP and “No HP” animals. (A) shows paired values for the wild-type strain N2; the 26 paired trials that were done as controls for all of the programmed cell death pathway experiments are shown. As shown in (B), egl-1 is not required for HP. egl-1(n3330) and egl-1(n1084 n3082), both null alleles, are significantly protected by HP. (C) ced-9 is not required for HP. Neither ced-9(n1950 gf) nor ced-9(lf) (full genotype: unc-69(e587) ced-9(n1950gf n2161lf); ced-3(n2433)) block HP. As shown in (D), ced-4 is required for HP. n1162, n1894, and n2274 carry stop-codon mutations in the ced-4 gene and probably represent null alleles [18]. The rescue strain has the genotype ced-1(e1735);ced-4(n1162);unc-31(e928);nEx7[unc-31(+);ced-4(+)]. As shown in (E), multiple ced-3 mutations do not block HP. (F) shows the summary of the effect of programmed-cell-death-pathway mutants on HP. The ratio of the percentage that are dead in HP to that for “No HP” in each trial are shown, mean ± SEM; dotted line indicates unity. ∗HP versus “No HP” significantly different by paired t test, p < 0.05.
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5. Figure 4 CED-4 Is Required Postdevelopmentally for HP
(A) A timeline of the experimental protocol is drawn to scale. Animals were exposed to ced-4(RNAi) or empty-vector control at the periods indicated. “Emb” stands for embryo.
(B) Comparison of HP protection for ced-4(RNAi) versus vector. ∗p < 0.05 compared to empty vector (paired t test); mean ± SEM of at least three independent trials, >50 animals per trial.
Current Biology  , DOI: ( /j.cub )
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